1. Field of the Invention
This invention relates to a new sulfur compound that contains a terphenyl skeleton. More particularly, the present invention relates to a sulfur compound that contains a liquid crystal terphenyl skeleton exhibiting high anisotropic factor of dipolemoment, which is useful as a novel functional thin film, with which the surface properties of the entire surface of the film can be reversibly controlled by applying an external stimulus such as an electric field, and dynamically changing the molecules and molecular aggregates that configure the self-assembled monolayer. The present invention further relates to a synthesisng method of such compound and to a self-assembled monolayer in which that compound is used, that contains a liquid crystal terphenyl skeleton exhibiting high anisotropic factor of dipolemoment, wherewith the surface properties of the entire surface of the film can be reversibly controlled by applying an external stimulus such as an electric field, and dynamically changing the molecules and molecular aggregates that configure the self-assembled monolayer.
2. Description of the Related Art
Conventionally, self-assembled monolayers (hereinafter called SAMs) that are formed when molecules spontaneously aggregate and are ordered merely by immersing a substrate of metal or the like in a solution of the target molecules have been developed in a wide range of fields. The most widely researched SAMs are organic sulfur SAMs such as alkane thiol SAMs and organic silane SAMs wherein a silane coupling agent is used. In particular, alkane thiols are chemical substances that spontaneously fabricate a SAM when a gold substrate (Au substrate) is immersed in an ethanol solution thereof. Systems resulting from combinations of metal films and thiol molecules play the central role in SAM research because of their stable chemical adsorbing properties and ability to form closely packed monomolecular film arrays.
Thiol derivatives having terphenyl skeletons used in SAMs are proposed, for example, in Sabatani, E., et al., Langmuir (1993), 9, 2974-2901, Himmel, H. J., et al., J. Am. Chem. Soc. (1998) 120, 12069-12074, and Ishida, T., et al., J. Phys. Chem. B. (1999) 103, 1686-1690.
With these thiol compounds, however, the packing of the molecular film readily takes on a herringbone structure due to the van der Waals intermolecular interaction between terphenyl moieties. When that happens, the molecular packing becomes stronger, and the 2-D (two dimensional) crystal structure of monolayer film on substrate also becomes stronger. This strong crystallinity becomes a large hindering factor in causing SAMs to move under the appropriate strength of an electric field using the high anisotropic factor of dipolemoment of the molecules. Thus there has been a need to develop compounds capable of forming SAMs that exhibit no crystallinity, and particularly SAMs that exhibit no crystallinity and at the same time exhibit liquid crystal properties (being fluid and exhibiting flexibility), while maintaining the high-degree of anisotropic factor of the dipolemoment.
Now, in Japanese Patent Application Laid-Open No. H9-255621/1997, certain compounds having a terphenyl skeleton are proposed as macromolecular dispersion type liquid crystal materials that exhibit high anisotropic factor of dipolemoment and that can be used in liquid crystal display elements. However, no example of the synthesis of a liquid crystal sulfur compound exhibiting high anisotropic factor of dipolemoment whereas maintaining the high-degree of chemical affinity to metal surfaces such as gold has been reported to date.
Accordingly, an object of the present invention is to provide a liquid crystal sulfur compound exhibiting high anisotropic factor of dipolemoment with strong affinity to metal surfaces.
As a result of various studies, the inventors discovered that sulfur compounds containing a terphenyl skeleton having a certain structure can achieve the object stated above, and thus arrived at the present invention.
Specifically, the present invention provides sulfur compounds containing the terphenyl skeleton represented by the general structural formula (I) given below. 
(where R1 is a nitrile group, halogen atom, hydrogen atom, methyl group, or trifluoromethyl group, R2 is a halogen atom, nitrile group, or trifluoromethyl group, R3 is 
or an alkyl group having 1 to 20 carbon atoms, n is a number from 1 to 20, and m is 0 or 1.